The old adage that gets repeated over and over is that an elephant never forgets. And to some degree, it’s true. Elephants have been shown to have some of the highest cognitive abilities in the animal kingdom, displaying the ability to recognize themselves in a mirror and to remember sources of food and water from decades past. But still, the saying might have picked the wrong animal.

Perhaps it should be, “A dolphin never forgets.”

Recent research has indicated that dolphins have personal “signature whistles” that are unique to each individual and serves – at least in part – as some sort of identifier in the wild. As individuals break off from their pods and join different groups, it would seem as though having the ability to recognize former friends apart from potential foes would be pretty useful. And indeed, studies have shown that signature whistles remain constant over time, are repeated throughout an individual’s life, and can elicit excitement and friendly responses from previous acquaintances.

Building off of these findings, one of the next logical questions for researchers to address was how long the memory of these “names” could last in a dolphin. What’s more, the steady population of dolphins living in captivity that get mixed and matched constantly throughout the world provided the perfect experimental setup.

While I was working at Six Flags in northeastern Ohio in the summers of college, we had four dolphins that made regular performances. After Cedar Point bought the park and shut it down (sad face), the dolphins got shipped off to different facilities throughout the world. If they got reunited today, would they still remember each other?

According to a recent study from the University of Chicago, most definitely.

Researchers recorded the signature whistles from many dolphins living in captivity across the globe. They then took those recordings and, using the immaculate records kept by the industry, went off to play the recordings for other dolphins who used to live with one another.

To start, the dolphins were played recordings of signature whistles from dolphins they had never met. To no surprise, they showed some initial mild interest, but soon lost attention and stopped checking out the speaker. But when they were then played the whistle of a former cohabitant, the response was completely different. The dolphins showed a lot more interest, got a lot more excited, responded in kind with their own whistle response, and refused to stop investigating the speakers.

And the memories seem to last a lifetime. Even dolphins that had been separated for more than 20 years had no trouble recognizing a signature whistle.

Keep in mind, however, that the use and memory of signature whistles might not be exactly what you think it is. It’s easy to project human experiences on other animals and assume that when a dolphin hears a signature whistle they know, an image of that whistle’s owner pops up in the dolphin’s head and they think of their friend in the same way that we think of an old classmate. Their reactions might not be so sophisticated. But that study is not far behind.

What’s more, on a final note, I would have liked the study to have been blind. In the experimental methods section, a thorough description is offered for how the researchers scored a dolphin’s reaction to a signature whistle. What wasn’t mentioned, however, was whether or not the researchers themselves knew which trials were former friends or completely unfamiliar. Might an excited dolphin researcher have over-scored a little bit and saw what they wanted to believe they’d see? It’s at least possible, and should probably be addressed.

The study, “Decades-long social memory in bottlenose dolphins,” was published in the Proceedings of the Royal Society B by Jason Bruck, who received his PhD this past summer from the University of Chicago’s Department of Comparative Human Development.